With the critical dimensions of the integrate circuits scaled down to deep sub micrometer stage, the surface cleanliness of the wafer during the IC manufacturing process is increasingly demanding. In order to ensure the high cleanliness, hundreds of cleaning processes are required in the IC fabrication, which takes up 30% of the whole manufacturing process.
Further statistics show that more than 50% of the defectives during the semiconductor manufacturing processes are caused due to the surface contamination and incomplete cleaning. In the cleaning process, liquid phase fluid is injected to the wafer through the nozzles positioned above the wafer. When the injection speed is high, a physical effect will be produced on the wafer surface. Under the high speed impact force of the fluid flow as well as the centrifugal force of the wafer rotation, the impurities and contaminants in the wafer surface grooves can be corroded, dissolved or suspended in the liquid phase fluid, and then removed with the fluid, so as to achieve the cleaning effects. However, the transmission capability of the impurities and contaminants to the main body of the liquid phase fluid is unsatisfying, which reduces the cleaning efficiencies and effects.
On the other hand, with the decreasing size of the patterned features on the wafer, the pattern damage caused by the high speed fluid injection cannot be overlooked. Since the conventional jet cleaning technology produces big-size droplets or jet streams, the damage to the patterned features on the wafer surface in the processes at 65-nanometer and below becomes more severe. Furthermore, the lower utilization of the liquid phase fluid may also lead to huge waste of resources.
Nowadays, a nanoscale jet cleaning technology has been studied to reduce such damage. By the nanoscale jet cleaning technology, the injected fluid is in an atomized form consisted of thousands of nanoscale droplets. The injected nanoscale droplets fall on the wafer surface from the nozzles and clean the impurities and contaminants in the patterned structures on the wafer surface. Although compared with the conventional cleaning technology which produces continuous fluid or big-size droplets, the nanoscale jet cleaning technology reduces the wafer surface damage to some extent, there still exist some problems. Since the atomized nanoscale droplets are injected to the wafer at a high speed as well, such droplets may easily enter into the internal patterned features of the wafer when contacting the patterned features directly due to their small size, which may cause the damage in a deeper level. Furthermore, since not all the droplets are injected perpendicular to the wafer surface, the oblique jet flow may result in greater damage to the sidewalls and the edges of the patterned features.
Accordingly, there is a need for a cleaning apparatus and method that is able to improve the transmission ability of the impurities and contaminants to the fluid in an atomized form while minimizing damage to the wafer.